The present invention relates to a fifth wheel coupling for the connection of a semitrailer to a tractor unit.
U.S. Pat. No. 3,352,571 discloses a fifth wheel coupling in which the king pin of the semitrailer is held by a kinematic locking mechanism of the tractor unit. The closing elements of the mechanism are two symmetrical, swivel-articulated closing jaws. In each of these jaws a semicircular recess is formed for seizing the king pin. The jaws can be swivelled back and forth between an opened position, releasing the king pin, and a locking position, seizing the king pin. One advantage of this design is the large contact area between the closing jaws and the king pin, so that only small surface pressures result and the wear is correspondingly small.
The large contact area between closing jaws and king pin has the character of a bearing of the king pin. The semicircular recesses of the closing jaws, joined together in the closed position of the closing jaws form a bearing shell; however, they must retain a certain play with respect to the king pin, because they must interact with a large number of different king pins. In addition, dirt can easily get onto the surfaces sliding against each other, in particular during coupling, which can then lead to a certain amount of wear.